Electron discharge device



NMA @9 l3 4 c. A. BODDIE ELECTRON DISCHARGE DEVICE Filed Nov. 5, 1930 .'5 Sheets--Sheefl l INVENTOR Clarmrenfaia'e.

ATTORNEY v .NMA @9 31%2 c. A. BODDIE ELEGTRON DISCHARGE DEVICE Filed Nov.

5 Sheets-Sheel 2 INVENTOR .ruw f i f ATTOR N EY Nov., 6, E934., c. A. BODDIE ELEGTRON DISCHARGE DEVICE Filed Nov. 5. 1930 3 SheetsFSheet 3 ATTORNEY Patented Nov. 6, 1934!! PATENT voFFlcF.

ELECTRON DISCHARGE DEVICE Clarence A. Boddie, Pittsburgh, Pa, assigner to Westinghouse Electric & Manufacturing Company, a corporation orlcnnsylvania Application November 5, 1930, Serial No. 493,506

13 Claims.

cuit which included lumped inductance andw lumped capacity, the lumped capacity being connected across the grid and plate electrodes.

Since the frequency at which the vacuumktubewould oscillate was increased by decreasing the value of the lumpedl capacity, the grid-plate capacity determined the maximum frequency at which energy could be generated.' With this type of high-frequency generator, therefore, the amount that the frequency of the current genero ated could be increased was limited ecause of the mechanical diiculties encountered in increasing the spacing between the grid and the plate to reduce the grid-plate capacity.

-An object of my invention is to provide an electron-discharge device of the above-mentioned 2 type which is so designed that the grid-plate capacity imposes no limitation upon the frequency of thecurrent thatl is generated.

More particularly, an object of my invention is to provide a vacuum tube in which the grid and plate elements form a portion of a trans-` mission line and in which the frequency of the generated'current is determined by the characteristics of said line.

A further object of my invention is to provide a structure of the above-mentioned type which has the desired electrical characteristics and which, at the same time, is so designed mechanically that it conforms to the preferred practice in constructing large power tubes. lo In practicing my invention, I employ two sim-V ilar three-element vacuum tubes, each tube com` prising an evacuated envelope having a metal wall which acts as anv anode, The anodes of the vacuum tubes are electrically connected by means of a metal pipe. The control electrodes of the vacuum tubes are also electrically connected by means of a second metal pipe. Since the outer pipe has a larger diameter -than that of the anodesV in order that it may extend over the glass end or blank of the tube, the diameter of the inner pipe is enlarged at the point where it extends beyond the glass blank. In this wayl the grid and plate electrodes and the two pipes form a transmission line which consists of tWO This dif--k (Cl. Z50-27.5)

concentric tubes the diameters of which have the same ratio throughout the length of the line. This forms a transmission line which has uniformly distributed inductance and capacity.

The outer pipe has a larger diameter than the anodes for mechanical reasons, while the inner pipe has a larger diameter than the control electrodes in order that the portion of the line which is formed by the two pipes may have an impedance which matches the impedance of' 65 that portion of the line which is formed by the grids and plates. The distance from the outer end of one anode to the outer end of the other anode determines the length of the standing wave which may be generated and, therefore, the frequency of the current which is generated by the oscillator.

Other features and advantages of my invention will appear from the following description, taken in connection with the accompanying drawings, in which,

Fig. 1 is a diagrammatic view, in longitudinal section, of a vacuum-tube oscillator constructed in accordance with my invention;

Fig. 2 isy a diagrammatic view of the electrical 80 connections employed in my invention.

Fig. 3 is a diagrammatic view of an oscillator to aid in explaining the operation of the circuit shown in Fig. 2;

Fig. 4 is a view, in longitudinal section, of the upper end of one of the vacuum tubes which are employed in the oscillator illustrated in Fig. 1;

Fig. 5 is a view, in longitudinal section, of the lower end of the vacuum tube shown in Fig. l

and of a portion of the pipes employed to conneet the two vacuum tubes;

Fig. 6 is a view, in longitudinal section, of ay portion of the pipes which are employed in connecting the Vacuum tubes;

Fig. '7 is a view, in lateral section, taken on the 95 line VII-VII of Fig. 4, and

Fig. 8 is a view of the upper end of the tube shown in Fig. 4..

Referring to Fig. 1, the apparatus comprises two similar three-electrode vacuum tubes. Each 10G, vacuum tube comprises an evacuated envelope 10 having an outer metallic wall 11 which acts as the anode. The metallic wall 11 is closed at each end by means of glass blanks 12 and 13. The anode 11 is provided with a water-coolingjacket 105 14. `The control electrode 15 is supported, at oneend, by means of the glass blank 13 while thelament 16 is supported from the glass blank 12. The anodes 11 of the two tubes are connected together by means of a cylindrical metallic pipeA 11o 17 which is supported at each end by means of the anode cooling jacket 14. Conductors 18 and 19 extend from the pipe 17 through openings in a metallic casing 20 which shields the apparatus to prevent radiation from the generator itself.

A circular metallic pipe 21 is positioned within the outer pipe 17. and supported, at each end, by means of a control electrode 15. A grid conductor 22 extends from the pipe 21 through openings in the pipe 17 and the casing 20.

Referring to Figs l4 to 8, the glass blank 12 includes three re-entrant portions 23, 24, and 25, in which are sealed metallic rods 26, 27 and 28, respectively. These rods are brought near to, but not in contact with, each other at the middle of the tube as shown in Fig. 4. The rod 28, which extends from the re-entrant portion 25, is hidden back of re-entrant portion 24 in Fig. 4. 'I'he rod 26 supports a rod 26 which is centrally located in the, tube.

The rods 27 and 28 support the filament wires 29 and act as the filament lead-in conductors. The lament wires 29 are supported from the rods 127 and 28 by means of heavy wires 27' and 28 ,ture more clearly.

An electrostatic shield 32 is clamped to each k of the rods 26, 27, and 28 to protect the seals.

The grid 15 comprises a plurality of metallic rods 33 which are arranged inthe form of a circular cage and which are held in position by means of metallic rings 34. The grid is supported at the end of the tube opposite the lament support by means of a metal-thimble 35 which has its edges sealed to the lower glass blank 13.

1The thimble 35 is externally threaded to hold an` electrostatic shield 36 in position over the seal. The thimble is internally threaded to provide a support for one end of the pipe 21.

The anode 11 may be provided with any suitable cooling means. In the apparatus illustrated, the cooling means comprises an outer wall 14 which is in the form of a circular pipe supported at its ends by means of annular metallic members 38 and 39. The annular members 38 and 39 are held in screw-threaded relation to the anode 11. The joint between the upper end of the wall 14 and the annular member 38 is made liquid tight by means of a gasket 40 which is clamped between the end of the wall 14 and a flanged' ring 41. The ring 41 ts over the annular member 38 and is split in halves.

'I'he joint between the lower end of the wall 14 and the annular member 39 is made liquid tight by means of a gasket 42 which is clamped between the wall 14 and a flanged ring 43. The ilanged'ring43 is slidably mounted on the annular member 39 to prevent breakage of parts caused by their unequal expansion when heated. An in let and an outlet for the cooling fluid are provided by the pipes 44 and 45. Y

An electrostatic shield 46 is bolted-to the flanged ring 41. 'I'he anode 11 is internally threaded at each end in order to support electrostatic shields 47 and 48.

Each end of the outer pipe 17, which acts as a section of a transmission line and Vwhich electrically connects the anodes of the twoV vacuum tubes, is bolted to one ofv the annular metallic members 38 and 39. It will be noted that the end of the pipe 17 is split to make it more readily t over the supporting member 39.

The pipe 2l' is increased in diameter, in effect, by terminating it at a point just beyond the glass blank 13 and by flexibly connecting thereto a pipe 21 of larger diameter. The pipe 21 is held in position at each end by means of a group of three quartz tubes 49 (Fig. 6). A good electrical contact between the pipes 21 and 21 is made certain by means of electrical conductors 50 which are clamped to the pipe 21 and held by means of soldering and a number of turns of wire on the larger pipe 21.

In order to match the impedance of the portion of the line formed by the vacuum-tube electrodes 11 and 15 with the impedance of the line formed by the pipes 17 and 2l connecting the two vacuum tubes, the parts are so proportioned that the ratio of the external diameter of the grid cage 15 to the internal diameter of the anode ll is substantially the same as the ratio of the external diameter of the pipe 21 to the internal diameter of the pipe 17. With this design, the two line portions mentioned above havethe same characteristic impedance, characteristic impedance being dened as the Value where L is the inductance and C the capacity per unit length of the line.

While the structure of the vacuum tube illustrated is such that there is necessarily a slight impedance irregularity between the grid 15 and the enlarged portion 21 of the inner pipe, this irregularity does not seriously affect the operation of the system, and the vacuum-tube electrodes and the pipes 17 and 21 will act as a line having uniformly distributed capacity and inductance.

Referring to Fig. 5, the glass blank 13 and the grid-supporting thimble 35 are cooled by means of a current of air which enters through the pipe 51 and, after being deflected by the baille 52, circulates around the blank 13, through the openings 53 in the pipe 21', through the opening 54 in the end of a baille tube 55, and through the pipes 21 and 2l. At the other end of the outer pipe 17, air is blown around the glass blank 13 of the other tube in a similar manner. The connection between the pipes 21 and 21 is made air tight by means of rings 56.

'I'he air leaves' the inner pipe 21 through the quartz tube 49 shown in Fig. 6. The inner end of each tube 49 is supported by a block 57 and inalignment with an opening 49'. The outer held in position by means of a cover plate 60. i

The cover plate is held to the main section of the pipe 17 by means of screws 61 and is soldered to the top half pipe 17 to form an electrical connection.

Referring to Fig. 2, the cathode 16 of each tube novaees a ferred when a line one-half 'wave length long is utilized, because the voltage is then applied i at the node of the standing voltage wave, as indicated by the dotted line 65.. In any case. a choke coil 66 is preferably inserted in the highvoltage conductor` 18.

The grids 15 are preferably connected to ground through a conductor 22, choke coil 67 and a ccn-v denser 68 and grid leak 69. As in the case of the connection of the plate system to the high-voltage supply, the grid system may be connected to ground at any point but it is preferably connect.

ed to ground at the middle of the inner pipe where the node of the standing wave is located.

A radiating system which may comprise an antenna 70 and counterpoise 71 vand tuningr incapacity 78 ductances 72 and 73, connected through a conductor 19' to a high-voltage point on the pipe or conductor 17. A radiating system of this character is described in U. S. Patent 1.652.516 issued to Westinghouse Electric 8a Manufacturing Company on December 13, 1927 upon an application filed by F. Conrad.

The operation of my high-frequency generator is analogous to the operation of the well known -circuit illustrated in Fig. 3. In Fig. 3, the generator comprises a three-electrode vacuum tube having a grid 74, a plate 75 and a filament 76. The frequency at which the system oscillates is determined by the natural period of an oscillatory circuit consisting of an inductance coil 77 and a condenser 78 connected in parallel thereto. 'Ihe filament 76 and the mid point of the inductance coil 77 are grounded. The grid 74 is connectedy to the inductance coil 77 at one side of the grounded point, and the plate 75 is connected to the inductance coil "17 on the opposite side of the grounded point. The necessary positive potential is supplied to the plate through a choke coil In the circuit shown in Fig. 2, the distributed inductance and capacity of the line formed by the grids 15 and the pipe 21 and the plates 11 and the pipe 17, replace the lumped inductance 77 and the of the circuit shown in Fig. 3. The oscillatory circuit shown in Fig. 2 does not have the direct connection to ground at any point but ,the system is allowed to have a floating. ground potential.

Since a vacuum tube is a high impedance device, it is necessary, for eiiicient operation, that the tube shall work into a circuit having a high impedance, preferably an impedance of the order .of that of the output of the vacuum tube. A transmission line, either a quarter-wave length or a half-wave length would give the required high impedance, but, in the case of a line a Quarter wave length, it would be necessary to short circuit the end of the line. Since this would require the use of a large condenser, a line which is one-half wave length is preferred.

' The system may b`e caused to generate higher frequencies than those indicated above by connecting an impedance unit across a certain portion of the transmission line, that is, between the pipes 17'and 21. As shown u in Fig. 2, this may be accomplished by closing the switch 80 to connect the' resistance unit 81 across the conductors 17 and 21.

A standing voltage wave will then be set up on .the line as indicated by thedotted line 82, a node being located at the point where the resistance unit 81 connects the conductors together. This result'is based on the principle that an oscillation generator will oscillate at that frequency for which .the system losses are the lowest.

Various modifications may be made in my invention .without departing. from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are shown by the prior art andare set forth in the appended claims.

I claim as my invention:

1. An electron-discharge device including an anode and a control electrode. two conductors therein havingy uniformly distributed inductance and capacity, andmeans connecting said anode to one of, said conductors and said control elec-v electron-discharge tube having an anode and/a control electrode which form a section of a transm/ission line therein having uniformly distributed capacity and inductance, a second section of a transmission line having uniformly distributed` capacity and inductance of unit values different from those of the first said section, means conductively connecting said transmission line sections, the characteristic impedances of said'sections being substantially equal.

3. An electron-discharge device including an evacuated vessel enclosing a cathode and having a metallic wall which acts as an anode, a member of insulating material sealing one end of said metallic wall, said member having larger lateral external dimensions than said Wall, a control electrode positioned within said vessel, a metallic tube surrounding said member and connected to said wall, and a second metallic tube positioned within saidrst-named tube and said insulating member (and connected to said control electrode.

4. A high-frequency generator comprising two electron discharge devices, each device including an evacuated vessel having a metallic wall which acts as an anode and a member of insulating material sealed to one end of said wall, said member having larger lateral externa1 dimensions than said wall, a cathode and a control electrode positioned within said vessel, a metallic tube surrounding said control electrode and connected to said wall, and a second metallic tube positioned within said first-named tube and said insulating member and connected to said control electrode, the iirst-named metallictubes of said devices being connected together at their free ends, and

said second tubes of said devices being connected said wall, and a second metallic tube positioned within said rst-named tube and said insulating member and connected to said control electrode, the spacing between said tubes being decreased at a point immediately beyond said insulating member.

6. A high-frequency generator comprising an evacuated vessel having a metallic wall which acts as an anode,` a control electrode and a cathode positioned within said vessel, said anode and said control electrode forming a portion of a line having substantially uniformly distributed inductance and capacity, two electrical conductors forming the other portion of said line, said anode being connected to one of said conductors and said control electrode being connected to the other of said conductors.

7. An electron discharge device including an evacuated vessel enclosing a cathode and having a metal wall which acts4 as an anode, a control electrode positioned within said vessel, a metallic tube connected to said anode, and a metallic tube positioned within said rst tube and connected to said control electrode, said tubes and electrodes forming an oscillating system, and means for connecting a source of direct current potential to said anode at a point one-quarter wave length from the end of said system.

8. An electron discharge device including an evacuated vessel enclosing a cathode and having a cylindrical metallic wall which acts as an anode, a member of insulating material sealing one end of said metallic wall, said member having a larger diameter than said wall, a control electrode of circular cross-section positioned within said vessel, a cylindrical metallic tube surrounding said member and connected to said wall, and a second cylindrical metallic tube positioned within said rst-named tube and said in'- sulating member and connected to said control electrode, the ratio of the diameter of said rstnamed tube to the diameter of said second tube at the region immediately beyond said insulating member being substantially'equal to the ratio of the diameter of said anode t0 the diameter ofsaid control electrode. n

9. An oscillation generator including conductors having substantially uniformly distributed capacity and inductance whereby a standing wave may be formed thereon, means for controlling the frequency of' the energy generated which comprises a resistor connected between said conductors at a point where a voltage node will be formed. p

10. An oscillation generator including conductors having substantially uniformly distributed capacity and inductance whereby a standing wave may be formed thereon, means for forming a standing wave on said conductors which has a wave length different from the fundamental wave length of said conductors, said means comprising an impedance unit connected between said conductors at a point where a voltage node will be formed.

11. An electron-discharge device including an evacuated vessel enclosing a cathode and having a metallic wall which acts as an anode, a member of insulating material sealing one end of said metallic wall, said member having larger lateral external dimensions than said wall, a control electrode positioned within said vessel, a metallic tube surrounding said member and connected to said wall, and a second metallic tube positioned 'within said rst-named tube and said insulating member and connected to said control electrode, the spacing between said tubes being decreased at a point immediately beyond said insulating member. i

l2. An electron-discharge device including an evacuated vessel enclosing a cathode and having a metallic wall which acts as an anode, a member of insulating material sealing one end of said metallic wall, said member having larger lateral external dimensions than said wall, a control electrode positioned within said vessel, a metallic tube surrounding said member and connected to said wall, and a second metallic tube positioned within said first-named tube and said. insulating member and connected to said control electrode, the characteristic impedance of the portion of the line formed by said tubes being substantially the same as that of the portion of the line formed by said anode and said control electrode.

13. A high-frequency'generator comprising an evacuated vessel having a metallic wall which acts as an anode, a control electrode and a cathode positioned within said vessel, said anode and said control electrode forming a portion of a line having substantially uniformly distributed inductance and capacity, two electrical conductors forming the other portion of said line, said anode being connected to one of said conductors and said control electrode being connected to the other of said conductors, said other portion of said line having a characteristic impedance which is substantially equal to the characteristic impedance of said first-named portion of said line.

CLARENCE A. BODDIE. 

